A California pollster seems to think that California still has Democratic primaries for US Senate? Sad!
What are you talking about? Feinstein gets 39% of Republicans according to the poll.
There's no way other is only 10% with just 2 Democrats.
Not seeing exact question wording, but usually in these cases, the only explicit options are the two candidates - Feinstein and DeLeon, plus undecided. If a voter says "other" despite being given only Feinstein/DeLeon as options, they record it as other, but they don't reveal other as being an available option when the question is being read to the voter, so most will hold their nose for one of the two candidates.
And of course, if this is the actual runoff, which is very conceivable, Feinstein will obviously win the republican vote bigly because she's not a berniecrat.